Devices converting electrical oscillations into acoustic waves, or vice versa, are known in various embodiments (cp. DE 31 04 860, DE 33 13 887, DE 35 25 724) namely in the form of telephone receivers which include an earpiece and a mouthpiece, connected together with a handle (cp. DE 33 41 251). The electro-acoustic conversion is performed by known measures, and, structurally, the converters typically include an assembly consisting of functional components inserted into multi-part housings. The housing parts do not operate as functional elements in the electro-acoustic conversion, but merely house the electro-acoustic converters and allow the sound waves, or electrical oscillations, to enter or emerge. For that purpose, acoustic windows in the form of perforated screens or the like are provided. However, the number of components in the converter on the one hand and the multi-part housing on the other is costly and time-consuming in terms of assembly and inventory. Flexible circuits, which include printed conductive traces, have been used in the area of electro-acoustic converters (cp. DE 29 06 893), however these have not contributed to a comprehensive simplification with respect to structure, manufacture or assembly. Wired circuits (cp. DE 33 41 251) are still typically used in practice.